And Saul sent messengers unto David's house
Supposing that he was gone thither; where this was is not said, very likely in Gibeah, where Saul lived:
to watch him;
that he might not get out from thence in the night:
and to slay him in the morning;
the reason why he did not order them to break into the house, and slay him at once, but wait till morning, seems to be, lest should he be alarmed by their breaking in, he might take the advantage of the night, and easily escape, or another person through mistake might be slain for him; and therefore, that they might be sure of him, they were to watch till it was broad daylight, when they could not well miss him. Josephus F4 says, the orders to watch him until morning were, that he might be taken and brought to a court of judicature, and be condemned and put to death, which was usually held in a morning; but Saul's orders to the messengers were to put him to death themselves, and he had no notion of dealing with him according to a formal process of judgment:
and Michal, David's wife, told him, saying, if thou save not thy life
tonight, tomorrow thou shalt be slain;
meaning, if he did not take the benefit and advantage of the night to make his escape, he would not be able to do it in the morning; the house being so beset, as she perceived, by persons whom she might suspect were sent by Saul to destroy him, knowing the ill will her father bore to him, or a messenger at the same time might be dispatched to her, either from her brother Jonathan, or from one of her friends at court, acquainting her with the design against David, and the danger he was in. Upon this occasion David penned the fifty ninth psalm, see ( Psalms 59:1-17 ) .
F4 Antiqu. l. 6. c. 11. sect. 4.